GB1218216A - Heat generating pipe - Google Patents

Abstract

1,218,216. Induction heating. CHISSO CORP. 15 May, 1968, No. 23142/68. Heading H5H. A ferromagnetic steel pipe or pipes is or are heated by currents induced in the inner wall portion thereof, the outer wall portion carrying substantially no current, an insulated conductor line or lines connected to an A.C. supply and extending within the entire length of the pipe(s) inducing said currents, the ends of the pipe(s) being interconnected by a conductor(s) of low impedance. The depth S in which the current flows is given by S = 50 30#e/Áf, and the following conditions are satisfied: t> 2S, D#S, l#D (e is the resistivity, Á the permeability, f the frequency, D the inside diameter, t the thickness, and I the length). In Fig. 6, insulated conductors 43, 43<SP>1</SP>, 43<SP>11</SP> from a 3- phase source 41 extend through three pipes 42, 42<SP>1</SP>, 4211 and are connected at star point 44. The ends of the pipes are interconnected by low impedance conductors 45, 46, 45<SP>1</SP>, 461. In Fig. 7, an insulated conductor 49 with a deltaconnection to 3-phase source 47 induces currents in a pipe 48 with five U-bends 50, 54, 50<SP>1</SP>, 55, 50<SP>11</SP>, the necks 51, 511, 51<SP>11</SP> being interconnected by low-impedance conductors 53, 53<SP>1</SP>. Alternatively, an insulated conductor from a singlephase source may extend through a single straight pipe (Fig. 3), a single U-shaped pipe (Fig. 4) or two straight parallel pipes (Fig. 5). The conductor insulation comprises natural or butadiene rubber, polyethylene, polypropylene, P.V.C., P.T.F.E., polyamide resin, polyester resin, glass fibres. For heating a liquid transportation pipe, e.g. for solid paraffin, asphalt, naphthalene, glacial acetic acid, concentrated caustic soda solution, oil, the heat-generating pipe may be bound to the transportation pipe pipe by metal bands or welding. The heatgenerating pipes may be embedded in concrete walls, floors, roads, runways.